Anything with a real strong odor, like pine, should be avoided. This is poisonous to snakes.

That said, aspen is always a good choice. It kinda depends on your preferences. If you like the look of the carpet and don't mind cleaning it, keep it. If you want the look of aspen and don't mind having the chips get in random places, go for it.

I have four snakes and find that newspaper or papertowels work the best for me. It incredibly easy to clean---out with the old, in with the new---and is cheap, too... especially if you have a subscription.